Implantable materials

ABSTRACT

A textured breast implant is provided which generally includes a fluid fillable elastomeric shell having a texture defined by struts, for example, hollow struts, defining interconnected open cells. Methods of making the texture include applying a silicone dispersion to a base material and removing the base material from the coating to form a silicone-based structure comprising struts defining interconnected open cells, said struts including internal surfaces defining cavities within the struts. The method may further include the step of contacting the silicone based structure having cavities with a silicone dispersion to cause the silicone to enter and fill the cavities.

This application claims priority to U.S. Patent Application No.61/375,686, filed Aug. 20, 2010, the entire disclosure of which isincorporated herein by this reference.

BACKGROUND

The present invention generally relates to medical implants and morespecifically relates to foam-like materials suitable for implantation ina mammal.

Prostheses or implants for augmentation and/or reconstruction of thehuman body are well known. Capsular contracture is a complicationassociated with surgical implantation of prostheses, particularly withsoft implants, and even more particularly, though certainly notexclusively, with fluid-filled breast implants.

Capsular contracture is believed to be a result of the immune systemresponse to the presence of a foreign material in the body. A normalresponse of the body to the presence of a newly implanted object, forexample a breast implant, is to form a capsule of tissue, primarilycollagen fibers, around the implant. Capsular contracture occurs whenthe capsule begins to contract and squeeze the implant. This contracturecan be discomforting or even extremely painful, and can cause distortionof the appearance of the augmented or reconstructed breast. The exactcause of contracture is not known. However, some factors may includebacterial contamination of the implant prior to placement, submuscularversus subgladular placement, and smooth surface implants versustextured surface implants, and bleeding or trauma to the area.

Surface texturing has been shown to reduce capsular contracture whencompared to what are known as “smooth” surface implants.

There is still a need for a more optimal surface textured implant thatfurther reduces the potential for capsular contracture. The presentinvention addressed this need.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a method of making amaterial suitable for implantation in a mammal. The method generallycomprises the steps of providing a base member including a poroussurface defined by interconnected pores and contacting the base memberwith a silicone-based fluid material in a manner to cause the fluidmaterial to enter the pores. In one embodiment, a vacuum is applied tothe base member to draw the fluid material into and/or through thepores. The method may comprise the steps of removing excess fluidmaterial from the base member to obtain a coating of the fluid materialon the porous surface, and allowing the coating to set to form asilicone-based structure suitable for implantation in a mammal. Theremoval process can be obtained using an airknife to blow away theexcess material, and/or squeezing out the excess material, and/or usingsuction to remove the excess material. The silicone-based structureincludes a porous surface, having interconnected cells, the poroussurface substantially identically conforming to the porous surface ofthe base member.

In one aspect of the invention, the base material is a material whichcan be degraded or otherwise removed from within the coating withoutsubstantially affecting the coating structure. In some embodiments, thebase material is a substantially biodegradable material. The basematerial may be polyurethane, for example, polyurethane foam.Alternatively, the base member is melamine, for example, melamine foam.Other base member materials are also contemplated and include, forexample, foams made from polyethylene, polyethylene vinyl acetate,polystyrene, polyvinyl alcohol, or generally a polyolefin, polyester,polyether, polyamide, polysaccharide, a material which contains aromaticor aliphatic structures in the backbone, as functionalities,crosslinkers or pendant groups, or a copolymer, terpolymer orquarternaly polymer thereof. Alternatively the material may be acomposite of one or more aforementioned materials. In another embodimentof the invention the base material can be a metal, for example a metalfoam, a ceramic, or a composite material.

The silicone-based fluid material may comprise a dispersion, forexample, a silicone dispersion, solution, emulsion or mixture. Thesilicone-based fluid material may be a solution of a room temperaturevulcanizing (RTV) or a high temperature vulcanizing (HTV) silicone fromabout 0.1-95 wt %, for example, about 1-40 wt %, for example, about 30wt %. In an exemplary embodiment, the silicone-based fluid material is ahigh temperature vulcanizing (HTV) platinum-cured silicone dispersion inxylene.

In another aspect of the invention, the base member, or at least aportion thereof, is removed from the silicone-based structure. In oneembodiment, substantially all of the base material is removed, such thata product is obtained which comprises or consists of material that issubstantially entirely pure silicone, for example, a porous, cellularsilicone foam. The step of removing may comprise, for example,contacting the base member with a solution capable of dissolving thebase member. For example, in an embodiment of the invention in which thebase member is polyurethane foam, the step of removing may comprisecontacting the base member with a hydrogen peroxide solution. In otherembodiments of the invention, the base material may be degraded byexposure to UV light, heat, oxidative agents, a base such as sodiumhydroxide, or an acid such as phosphoric acid or a combination thereof.The material may be exhaustively removed further by a secondary processsuch as solvent leach or vacuum.

In another aspect of the invention, a material suitable for implantationin a mammal is provided. The material comprises a porous, cellularmember comprising a silicone-based structure. The silicone-basedstructure has a topography, for example, a pore size, shape andinterconnectivity, substantially identical to that of a polyurethanefoam. This material may be made by the processes in accordance withmethods of the invention, as described herein.

In yet another aspect of the invention, a method of making a materialsuitable for implantation in a mammal is provided which generallycomprises providing a base member comprising a degradable foam andincluding a porous surface defined by interconnected pores, and coatingthe base member with a substantially non-biodegradable polymericmaterial to obtain a substantially non-biodegradable polymeric structuresuitable for implantation in a mammal. More specifically, the methodincludes contacting the base member with a fluid precursor of thesubstantially non-biodegradable polymeric material in a manner to causethe fluid precursor to enter the pores, removing excess fluid precursormaterial to obtain a coating of the fluid precursor on the base member,and allowing the coating to set to form the substantiallynon-biodegradable polymeric structure. The resulting structure includesa porous surface substantially identically conforming to the poroussurface of the base member.

In yet another aspect of the invention, a method is provided whichgenerally comprises providing a base member including a porous surfacedefined by interconnected pores, contacting the base member with a firstmaterial, allowing the first material to set to form a first materialcoating on the base member, contacting the first material coating with asecond material different from the first material and allowing thesecond material to set to form a layered polymeric structure suitablefor implantation in a mammal. The resulting layered polymeric structureincludes a porous surface substantially identically conforming to theporous surface of the base member. In an exemplary embodiment, the firstmaterial is a fluorinated polyolefin material and the second material isa silicone dispersion.

In yet another aspect of the invention, a method of making a material isprovided, the method generally comprising the steps of providing a basemember having a surface defined by a geometry including interconnectedpores, forming a first coating on the surface of the base membermaterial, the first coating being selected from the group of materialsconsisting of polystyrene, polyethylene-co-vinyl acetate, and poly(styrene-co-butadiene-co-styrene), and removing the polymeric basemember by contacting the base material with a material that will causethe base member to be removed from the first coating without causing anysubstantial degradation of the first coating. Next, a silicone-basedfluid material is applied to the first coating which now has the basemember removed therefrom, and cured to form a silicone coating on thefirst coating. The first coating is then removed from the siliconecoating, for example, by dissolving away the first coating from thesilicone, thereby forming a silicone foam-like material.

Each and every feature described herein, and each and every combinationof two or more of such features, is included within the scope of thepresent invention provided that the features included in such acombination are not mutually inconsistent.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be more clearly understood and certain aspectsand advantages thereof better appreciated with reference to thefollowing Detailed Description when considered with the accompanyingDrawings of which:

FIG. 1 is an SEM micrograph of a implantable material made in accordancewith a method of the invention; and

FIGS. 2-9 are images of other materials that can be useful as basematerials in accordance with different embodiments of the invention.

FIG. 10 is a SEM image of a base material, specifically a polyurethanefoam material at 500× magnification, useful in the manufacturing of someof the silicone-based materials of the present invention.

FIG. 11 is a polyurethane foam material such as shown in FIG. 10, nowcoated in silicone in accordance with certain embodiments of theinvention, at 500× magnification.

FIG. 12 is an image similar to that shown in FIG. 11, except a moreviscous silicone has been applied to the polyurethane, resulting in moresilicone being deposited, relative to that shown in FIG. 11.

FIG. 13 is a substantially hollow, foam-like silicone material (shown at400× magnification) in accordance with the invention, after apolyurethane material has been removed from (e.g. leached out of) thesilicone coating, leaving voids or hollows in the struts and cell wallsof the foam-like silicone material.

FIG. 14 is a foam-like silicone material (shown at 400× magnification),in accordance with another aspect of the invention, after a siliconematerial such as shown in FIG. 13 has been contacted with additionalsilicone, thus filling the voids left by the removed polyurethanematerial.

FIGS. 15A-15H are SEM images of various silicone-based foam-likematerials in accordance with embodiments of the present invention.

DETAILED DESCRIPTION

The present invention generally pertains to foam-like materials, forexample, biocompatible, foam-like materials, for example, implantablematerials and methods of forming same. The materials are useful for avariety of purposes, including, but not limited to, use in medicalenvironments.

In one aspect of the invention, methods are provided for making animplantable material that is substantially biologically inert and/orsubstantially non-biodegradable, which has a structure, for example, amicrostructure, similar or substantially identical to that of a foam ofa different material. The different material may be, or may not be, abiologically inert or non-biodegradable material.

In a specific embodiment, the foam-like materials are substantiallyentirely comprised of silicone yet have the topographical structure of anon-silicone material, for example, a polyurethane foam.

For example, a material in accordance with one embodiment is a flexible,soft, silicone-based foam-like material having substantially the same orsubstantially identical geometry of a polyurethane foam, but with thechemical inertness and biocompatibility of a silicone.

For example, a method for making a foam-like material substantiallyentirely comprised of silicone generally comprises the steps ofproviding a base member, for example a polyurethane base memberincluding a porous surface defined by interconnected pores andcontacting the base member with a silicone-based fluid material. Thecontacting step is done in a manner to ensure coating of the base memberwith the silicone material in a manner to cause the fluid material toenter the pores and conformally coat the surfaces of the base material.In some embodiments, a vacuum may be applied to the base material inorder to facilitate the contacting step. Excess fluid material may beremoved from the base member to obtain a fine coating of the fluidmaterial on the porous surface of the base material. The silicone-basedcoating is allowed to set. The coating steps may be repeated once,twice, three or more times, for example, up to 1000 times, until adesired thickness and/or final foam density is achieved. In someembodiments, the underlying polyurethane material may be removed fromthe coating structure. For example, the polyurethane is contacted with adissolvent, dimethyl sulfoxide, or a degradant such as hydrogen peroxideor hydrochloric acid, followed by a dissolvent such as dimethylsulfoxide of dimethyl formamide or acetone. The resulting silicone-basedmaterial is flexible and biocompatible and includes a porous surfacesubstantially identically conforming to the geometry of a porous surfaceof a polyurethane foam.

It is to be appreciated that for a base material other thanpolyurethane, said base material can be removed by a solvent or othermeans, known to those of skill in the art, suitable for removing thebase material from the coating without substantially altering oraffecting the coating structure.

The base material may have a pore size of about 100-1000 μm (RSD, i.e.relative standard deviation, of about 0.01-100%); an interconnectionsize of about 30-700 μm (RSD of 0.01-100%); interconnections per pore ofabout 2-20(RSD of 0.01-50%); and an average pore to interconnection sizeratio of about 3-99%.

In some embodiments, the base material has a pore size of about 300-700μm (RSD of 1-40%); an interconnection size of about 100-300 μm (RSD of1-40%); interconnections per pore of about 3-10 (RSD of 1-25%) and anaverage pore to interconnection size ratio of about 10% to about 99%.

In an exemplary embodiment, the base member comprises a material, forexample, polyurethane or other suitable material, having a pore size of472+/−61 μm (RSD=13%), interconnection size: 206+/−60 μm (RSD=29%),interconnections per pore: 9.6+/−1.8 (RSD=19%), Pore to interconnectionsize ratio of about 44%.

The base material may be a foam with between about 20 ppi to about 150ppi, for example, between about 60 ppi to 100 ppi, for example, about 80ppi. In a specific embodiment, the base material is a polyurethane foamwith about 100 ppi.

The base material may have a thickness of between about 1 mm to about 5mm. In a specific embodiment, the base material has a thickness of about3 mm.

The base member may comprise any suitable porous material having thedesired surface structure. Alternative to polyurethane, the base membermay comprise melamine, for example, melamine foam. FIG. 2 is an SEMmicrograph of a melamine foam having a topography defined by highlyinterconnected, open pores. Other base member materials useful in themethods of the invention are also contemplated and include, for example,polyethylene foam, Styrofoam, or general polyolefin foams,polysaccharide foams, polyamide foams, polyacrylate foams, metal and/orceramic foams, and combinations thereof.

Porous surfaces of base member materials having a variety of surfacegeometries useful in accordance with various embodiments of theinvention are shown in FIGS. 2-9. More specifically, FIG. 2 is a SEMmicrograph of a melamine foam. FIG. 3 is a SEM image of a polyurethanefoam; FIG. 4 is an alumina aerogel foam; FIG. 5 is another aerogel, forexample, silica aerogel foam; FIG. 6 is a silica foam; FIG. 7 is a HiPfoam; FIG. 8 is a magnesium ceramic foam; and FIG. 9 is another ceramicfoam.

In an exemplary embodiment, the silicone-based fluid material maycomprise a dispersion, for example, a silicone dispersion, for example,a room temperature vulcanizing (RTV) or a high temperature vulcanizing(HTV) silicone dispersion. In an exemplary embodiment, thesilicone-based fluid material is a high temperature vulcanizing (HTV)platinum-cured silicone dispersion in xylene or chloroform. Thesilicone-based fluid material may be commercially available HTV siliconesuch as NuSil MED 4714. Percent solids in the coating dispersion aregenerally between about 15% to about 40%, for example, about 15%.

In some embodiments, the non-biodegradable polymeric structure, forexample, the silicone structure, may have a weight of at least about 3times, for example, at least 5 times for example, up to 10 times ormore, the weight of the base member coated thereby. In some embodiments,the silicone structure has a weight of between about 3 times and about10 times the weight of the based member coated thereby and is formedfrom only a single coating of the silicone dispersion, for example, asingle contacting step. For example, the percent pickup of some of thepresent methods is between about 300% and about 1000%, where “percentpickup” is defined as the % weight gain of the coated material versesthe starting weight of the base material. Therefore a 100% pickup of acoating would be where the coated material is the same weight as theinitial base member. For example, if the base member is 3 grams ofpolyurethane and the cured silicone coating on the base member is 3grams of silicone, 100% pickup has been achieved.

In some methods of the present invention, up to 1000% pickup isachieved. For example, a 70 mm diameter round of polyurethane having aweight of 0.3 g, may be coated with silicone in accordance with thepresent methods with a resulting silicone coated polyurethane having aweight of approximately 3.3 grams, i.e. 1000% pickup. In someembodiments, 300% up to 1000% pickup is achieved using only a singlecoating step in accordance with the methods of the present invention.

Alternatives to silicone-based polymers are also contemplated. Forexample, any implantable material that can be cured by crosslinking,thermoplastics that set by change in temperature, material that set byremoval of solvents or any elastomer that cures or sets by any knownmechanism, can be used. It is further contemplated that otherimplantable materials useful in accordance with the invention includesuitable metals or ceramics.

In another aspect of the invention, methods are provided for makingporous materials, for example, flexible, porous silicone-basedmaterials, for example, foam-like materials made substantially entirelyof silicone. In one embodiment, a method of making a material isprovided comprising the steps of providing a base member including aporous surface defined by interconnected pores, and contacting the basemember with a fluid first material, for example, a non-silicone basedmaterial, in a manner to cause the fluid first material to enter thepores. The first material is allowed to set to form a first materialcoating on the base member and the first material coating is contactedwith a fluid silicone-based material, for example a silicone dispersion.The fluid silicone-based material is allowed to set to form asilicone-based material coating on the first material coating, therebyforming a layered polymeric structure defined by a surface substantiallyidentically conforming to the surface of the base member. In a specificembodiment, the first material is a fluorinated polyolefin material.

In yet another aspect of the invention, a method of making a materialsuitable for implantation in a mammal is provided which generallycomprises providing a base member comprising a degradable foam andincluding a porous surface defined by interconnected pores, and coatingthe base member with a substantially non-biodegradable polymericmaterial to obtain a substantially non-biodegradable polymeric structuresuitable for implantation in a mammal. For example, the base member maycomprise a polyurethane foam. The substantially non-biodegradablepolymeric material can be any suitable biocompatible polymer and may beselected from a list of highly impermeable systems, such as but notlimited to, fluorinated polyolefins, to prevent diffusion of chemicalentities which may facilitate the degradation of polyurethane.Alternatively the fluorinated polyolefin can be coated as a base layer,prior to the final application of the silicone to act as a barrierlayer.

In another embodiment of this invention, the base member of a preferredgeometry, that is not dissolvable (for example, a crosslinked polymerhaving a porous surface) may be coated by a robust but dissolvablematerial, such as, for example, a foam material selected from the groupof materials consisting of polystyrene, polyethylene-co-vinyl acetate,and poly(styrene-co-butadiene-co-styrene). The base member, e.g. thenon-dissolvable foam, can then be removed from the dissolvable materialcoating, for example, degraded by relatively aggressive means, forexample, by acid digestion in 37% HCl, leaving the robust butdissolvable material behind. An implantable material of interest, forexample, a silicone-based fluid material, is deposited on the robust butdissolvable foam, for example, using the methods described elsewhereherein. The silicone-based fluid material may be in the form of adispersion having a solvent system that does not dissolve the robustpolymer. The silicone is allowed to set or cure, and the robust materialis then dissolved out by means which does not affect the material ofinterest (e.g. silicone), for example, by dissolution in acetone in thecase of polystyrene. In this case, the material of interest is notsubjected to aggressive conditions used to dissolve the original foam.

The present invention also provides a silicone-based foam-like materialsuitable for implantation, wherein the material generally comprises aporous silicone-based structure including struts defining interconnectedcells. The material may be substantially entirely silicone yet have theconfiguration of a polyurethane foam.

In some embodiments, the struts are substantially hollow, for example,the struts which define the pores of the foam-like material includeinternal surfaces defining cavities within the struts. This structuremay be made by some of the processes described elsewhere herein. Thecavities within the struts are negative spaces left behind after removalof a base foam material from a conformal coating of silicone.

For example, FIG. 10 is an SEM image (500×) of polyurethane foam, usefulas a base material in accordance with the invention. FIG. 11 shows animage of a polyurethane strut having a relatively thin coating ofsilicone in accordance with embodiments of the invention. A strut of thecomposite material has been cut for this image in order to reveal thebase material (polyurethane) within a silicone coating. FIG. 12 is asimilar view of a similar silicone-based, foam-like material, with arelatively thicker coating of silicone. The thicker coating may beaccomplished by using multiple coatings of a relatively low viscositysilicone dispersion or by a single coating of a relatively thicker, moreviscous silicone dispersion.

Turning now to FIG. 13, and SEM image of a similar silicone-based,foam-like material such as shown in FIG. 11, is shown, now after removalof foam base material from a silicone coating. The silicone structure,in accordance with this aspect of the invention, thus includes strutsdefining interconnected cells, and the struts include internal hollows,cavities or voids left behind by the removed base foam. Advantageously,this silicone, foam-like structure may be substantially entirelycomprised of, or essentially consist of, silicone, but has a structureclosely similar to a true polyurethane foam.

In yet other embodiments, a silicone-based structure may be providedwhich include struts defining interconnected cells, which are nothollow, but substantially solid. For example, the structure inaccordance with this embodiment may be made by the filling in thehollows or cavities left behind by the removed base foam.

For example, FIG. 14 shows a leached silicone-based foam-like material(as in FIG. 3) that has now been contacted with a silicone dispersion,thereby substantially filling in the voids left behind by the removedbase material. The material may have a reduced pore size andinterconnection diameter in comparison to the base foam, for example, anincreased volume to void space. For example, the pore size of theresulting silicone foam-like material may be between about 0.1% to about100% reduced relative to the base foam which was used to form thesilicone foam-like material. The interconnection diameter may range fromabout 0.1% to 80% of the initial base foam material. In a specificembodiment, the interconnection diameter is about 30% to 50% of theinitial base foam material interconnection diameter.

FIGS. 15A-15H are SEM images of various materials made in accordancewith methods of the present invention. More specifically, FIGS. 15A-15Bare SEM images of top and cross-sectional views, respectively, of asilicone-based material made in accordance with the invention; FIGS. 15Cand 15D are SEM images of top and cross-sectional views, respectively,of another silicone-based material (strengthened once with 10% MED 4815in Xylene); FIGS. 15E and 15F are SEM images of top and cross-sectionalviews, respectively, of another silicone-based material (strengthenedtwice with 10% MED 4815 in Xylene; FIGS. 15G and 15H are SEM images oftop and cross-sectional views, respectively, of another silicone-basedmaterial (strengthened thrice with 10% MED 4815 in Xylene, made inaccordance with the invention.

Example 1

A polyurethane open celled foam is coated according to the currentinvention using a solution of Silicone HTV 30% w/v, by either dippingthe polyurethane foam in the solution, casting the solution on a sheetof polyurethane or spraying the solution in excess over the sheet ofpolyurethane. The excess solution is removed by squeezing out the foam,or by vacuum at between about 20 in. Hg to about 40 in. Hg, or higher,which may be applied in any suitable manner, for example, through aBuchner funnel at the bottom of the foam (in the case of casting thesolution over the foam) or by blowing air over the foam as in the caseof an air-knife, or in combination of any of the aforementioned. Airpressure may be applied with a pressure in a range of about 20 to about100 psi. The foam is then devolitilized in vacuum or by application ofmild heat in the case of HTV, such that the solvent is removed, but theHTV is not cured. This can be achieved in the application of the aircurrent during the previous step (the air may or may not be heated).Finally the coated foam is cured and the coating layer is affixed untothe foam. Curing is done at a suitable curing time and temperature, forexample, for about 60 minutes at a temperature between about 120° toabout 150° C., depending on the materials used. The aforementionedcoating, removing, devolitizing and curing process may be repeated oneor more times, for example, up to 5 times for example, up to 10 times,for example, up to 20 times, for example, up to 50 times, for example,up to 200 times, for example, up to 500 times, for example, up to 1000times, to achieve various builds and/or final pore densities. Thepolyurethane may then be completely removed from the center of thesilicone structure by digestion in hydrogen peroxide/water solution withor without the presence of metal ions and with or without heating.Alternatively the polyurethane foam can be degraded out by 37% HCldigestion for 1-5 minutes, with vigorous agitation and air removal tofacilitate the uniform digestion of the polyurethane, and a subsequentDMSO wash to remove the remnant degradants which are not soluble in the37% HCl. The degradation/leaching steps can be repeated 1-20 times toachieve various levels of purity. The resulting material is asubstantially pure silicone foam useful as a surgical implant.

Example 2

A sheet polyurethane open celled foam (20×20 cm) is placed in acontainer the bottom of which is a fine grate. Vacuum is applied to thebottom of the grate to pull air through the top of the foam into thefoam and finally through the grate and out. A solution of about 20% HTV(platinum cured) in chloroform is cast over the foam and pulled throughthe foam by the vacuum, a jet of air is applied to the foam through anair-knife to remove any remaining solution droplets that are trapped inthe foam to clean out the pores. The foam is then devolitized in vacuumat about room temperature for 2 hours. The devolitized foam is finallycured at 120° C. for 1 hour. The process is repeated 3 times. Theresulting foam is an open celled polyurethane base foam, conformallycoated by an approximately 50 μm layer of silicone.

Example 3

An implantable material is produced substantially in accordance withExample 2, except that instead of a polyurethane foam, a melamine foamis used as the base member. In addition, the base material is notremoved from the silicone foam. The resulting implantable materialcomprises a highly porous, open celled structure having a melamine baseand a silicone overcoat.

Example 4

The silicone foam of Example 1 is produced as a flexible sheet. Thesheet is cut and laminated to form a front surface of a breast implant.The front surface of the breast implant has a surface texturesubstantially identical to a surface texture of a polyurethane foam, butis substantially pure silicone.

Example 5

A 20×20 cm sheet polyurethane open-celled foam of 100 ppi and athickness of about 3 mm, is placed on a fine grate. Vacuum (about 29 in.Hg) is applied to the bottom of the grate to pull air through the foamand grate. A solution of about 15% HTV Silicone (NuSil MED 4714)(platinum cured) in Xylene is cast over the foam and pulled through thefoam by the vacuum. A jet of air (about 100 psi) is applied to the foamthrough an air-knife to remove any remaining solution droplets that aretrapped in the foam and to clean out the pores. The coated foam is thendevolitized in vacuum at about room temperature for 2 hours. Thedevolitized foam is finally cured at 126° C. for 1 hour. The abovedescribed process is repeated 5 times. The cured silicone-coated foam iscontacted with dimethlysulfoxide and is placed in a shaker and agitatedat room temperature overnight to remove the polyurethane. The resultingstructure is an porous open-celled silicone member having a structureclosely matching the original polyurethane foam and made up of hollowstruts (hollows formed by the removed polyurethane) having asubstantially uniform wall thickness of about 80 μm.

Example 6

A 20×20 cm sheet polyurethane open-celled foam of 80 ppi and a thicknessof about 3 mm, is placed on a fine grate. Vacuum (about 29 in. Hg) isapplied to the bottom of the grate to pull air through the foam andgrate. A solution of fluorinated polyolefin is applied to the foam andallowed to set to form a fine coating of about 50 microns in thicknesson the foam. A solution of about 15% HTV Silicone (NuSil MED 4714)(platinum cured) in Xylene is cast over the fluorinated polyolefincoated foam and pulled through the foam by the vacuum. A jet of air(about 100 psi) is applied to the foam through an air-knife to removeany remaining solution droplets that are trapped in the foam and toclean out the pores. The coated foam is then devolitized in vacuum atabout room temperature for 2 hours. The devolitized foam is finallycured at 126° C. for 1 hour. The step of applying a solution of siliconedispersion is repeated until a cured silicone coating thickness of about100 microns is achieved.

Example 7

A porous open-celled silicone member having hollow struts is made asdescribed in Example 5. This foam-like silicone member is placed on agrate and is contacted with a silicone dispersion during application ofa vacuum. The silicone dispersion is allowed to devolitize and thesilicone dispersion application may be repeated, for example, up to fiveor more times. The resulting structure is a biocompatible,non-biodegradable foam-like material that has a structure, flexibilityand/or elasticity quite similar to a biodegradable polyurethane foam.

Example 8

The porous open-celled silicone member having hollow struts is made asdescribed in Example 7. This foam-like silicone member is then layeredonto a smooth breast implant shell using a suitable biocompatibleadhesive. The implant has a reduced likelihood of promoting capsularcontracture when implanted in a patient, relative to an implant having asmooth shell without the open-celled silicone member adhered thereto.

While this invention has been described with respect to various specificexamples and embodiments, it is to be understood that the invention isnot limited thereto and that it can be variously practiced within thescope of the invention.

1. A silicone-based material suitable for implantation in a mammal, thematerial comprising: a porous silicone-based structure comprising strutsdefining interconnected open cells, said struts including internalsurfaces defining cavities within the struts.
 2. The material of claim 1wherein the cavities are formed by removal of a different material fromthe silicone-based structure during manufacture of the silicone-basedmaterial.
 3. The material of claim 1 wherein the cavities are formed byremoval of a polyurethane foam from the silicone-based structure duringmanufacture of the silicone-based material.
 4. The material of claim 1wherein the silicone-based structure has a geometry substantiallysimilar to that of a polyurethane foam.
 5. The material of claim 1 madeby the process of: providing a base member including a porous surfacedefined by interconnected pores; contacting the base member with afluid, silicone-based dispersion; curing the silicone-based dispersionto form a silicone-based coating on the base member; and removing thebase member from the silicone-based coating to form said silicone basedstructure.
 6. The material of claim 5 wherein the process furthercomprises the step of applying a vacuum to the base member andsilicone-based material in a manner to cause the silicone-based materialto enter the pores and form a silicone-based coating on the poroussurface.
 7. The material of claim 6 wherein the process furthercomprises the step of allowing the silicone-based coating to devolitizewhile the vacuum is being applied.
 8. The material of claim 1 with about100 pores per inch (ppi).
 9. The material of claim 1 having a thicknessof between about 1 mm and about 5 mm.
 10. The material of claim 1 havinga thickness of about 3 mm.
 11. The material of claim 5 wherein thedispersion is about 15% to about 40% by weight percent solids.
 12. Thematerial of claim 5 wherein the dispersion is about 15% by weightpercent solids.
 13. The material of claim 6 wherein the vacuum isapplied at about 20 to about 40 Hg negative pressure.
 14. The materialof claim 6 wherein the vacuum is applied at about 29 Hg or greaternegative pressure.
 15. The material of claim 16 wherein the struts aresubstantially hollow.
 16. A method of making a material suitable forimplantation in a mammal, the method comprising: providing a base memberincluding a porous surface defined by interconnected pores; contactingthe base member with a fluid silicone-based material in a manner tocause the fluid material to enter the pores; applying a vacuum to thebase member to draw the fluid material into the pores; removing excessfluid material from the base member to obtain a coating of the fluidmaterial on the porous surface; and allowing the coating to set;removing the base material from the coating after allowing the coatingto set to form a silicone-based structure comprising struts defininginterconnected open cells, said struts including internal surfacesdefining cavities within the struts; contacting the silicone basedstructure having cavities within the struts with a silicone dispersionto cause the silicone to enter and fill the cavities.
 17. The method ofclaim 16 wherein the base member is polyurethane foam.
 18. The method ofclaim 16 wherein the coating has a thickness of between about 10 micronsand about 100 microns.
 19. The method of claim 16 wherein the coatinghas a thickness of about 50 microns.
 20. A breast implant comprising: afluid fillable elastomeric shell comprising a porous silicone-basedstructure comprising struts defining interconnected open cells, saidstruts including internal surfaces defining cavities within the struts.